This invention relates to certain phosphite and phosphate esters of 5-norbornene-2-methanol which are useful as antiozonants in chloroprene polymers.
Although elastomeric chloroprene polymers are exceptionally resistant to attack by atmospheric ozone, it is desirable for certain applications (such as, for example, flexing or stretching at elevated temperatures) to further reduce their ozone susceptibility. U.S. Pat. No. 3,563,947 to Gruber discloses a class of 5-norbornen-2-yl compounds having high antiozonant activity in such applications.
A class of hexachloronorbornenylmethyl phosphates has recently been disclosed in German Offenlegungschrift No. 2,243,006. Those compounds are useful as flame retardants for plastics.
While the synthesis of most phosphorus acid esters is quite simple, side reactions occassionally complicate the preparation of some of them. This is especially so in the case of trivalent phosphorus compounds, which frequently undergo spontaneous oxidation to pentavalent phosphorus compounds when the reaction is carried out in the presence of air.